It has been revealed by experiments using mice that Mx protein is induced when cells are stimulated with interferon, and that it is an important protein in exerting resistance to influenza virus infection [Proc. Natl. Acad. Sci. USA, 80, 1910-1914 (1983), Cell, 44, 147-158 (1986) and Cell, 62, 51-61 (1990)]. Thereafter, it was found that two types of protein, MxA and MxB, homologous to the mouse Mx protein, are also induced in human when cells are stimulated with interferon [Mol. Cell. Biol., 9, 5062-5072 (1989) and J. Virol., 64, 1171-1181 (1990)]. Infection experiments using influenza virus A and vesicular stomatitis virus have revealed that MxA inhibits viral growth in cells but MxB does not have the inhibition activity [J. Virol., 64, 3370-3375 (1990)].
A monoclonal antibody to MxA was first prepared by immunizing mice with the purified protein [J. Interferon Res., 7, 331-343 (1987)]. Thereafter, Towbin et al. prepared 5 monoclonal antibodies using recombinant MxA expressed in Escherichia coli as an immunogen [J. Interferon Res., 12, 67-74 (1992)]. It was confirmed by enzyme immunoassay (ELISA) and Western blotting that the monoclonal antibodies of Towbin et al. reacted with MxA, and they could be divided into those which recognize an epitope corresponding to amino acids 1 to 429, counting from the N-terminus, and those which recognize another epitope corresponding to amino acids 430 to 662.
Recently, with the advance in studies on the structure and function of Mx protein, it has been revealed that the Mx protein has a GTP-binding domain and GTPase activity, which are now regarded as important factors in relation to the anti-virus activity [Trends in Cell Biology, 3, 268-272 (1993)]. Also, the possibility has been suggested that Mx protein has a self-assembly motif and forms a large complex body through association of its molecules making use of the motif, thereby exerting its anti-virus function [J. Biol. Chem., 268, 15033-15038 (1993)].
Detailed elucidation of relationship between structure and function of Mx protein will make possible the accurate diagnosis of viral infectious conditions which are reflected by such a relationship. In the case of the known monoclonal antibodies which recognize MxA, it is difficult to elucidate the relationship of their functions with the GTP-binding domain and self-assembly motif because of the vague specificity of the binding site. Thus, accurate diagnosis of viral infectious conditions cannot be made. In addition, there are no reports of monoclonal antibodies capable of recognizing MxA which is intracellularly induced solely by viral infection, not by artificial stimulation with interferon.
The present invention relates to a monoclonal antibody which recognizes an epitope corresponding to amino acids 10 to 220, amino acids 221 to 297 or amino acids 469 to 662, counting from the N-terminus of a human Mx protein MxA, that specifically reacts with the human Mx protein by western blotting, immunoprecipitation or immunocyte staining and to a hybridoma which produces that antibody.